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Adsorption removal of Co(II) from waste-water using graphene oxide
HYDROM-04209; No of Pages 7 Hydrometallurgy xxx (2015) xxx–xxx
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Hydrometallurgy journal homepage: www.elsevier.com/locate/hydromet
Adsorption removal of Co(II) from waste-water using graphene oxide Lakshmi Prasanna Lingamdinne a, Janardhan Reddy Koduru b,⁎, Hoon Roh a, Yu-Lim Choi a, Yoon-Young Chang a,⁎, Jae-Kyu Yang c,⁎ a b c
Department of Environmental Engineering, Kwangwoon University, Seoul 139-701, Republic of Korea Graduate School of Environmental Studies, Kwangwoon University, Seoul 139-701, Republic of Korea Division of General Education, Kwangwoon University, Seoul 139-701, Republic of Korea
a r t i c l e
i n f o
Article history: Received 22 May 2015 Received in revised form 19 October 2015 Accepted 23 October 2015 Available online xxxx Keywords: Adsorption Graphene oxide Co(II) removal Heavy metal XRD and XPS studies
a b s t r a c t Graphene oxide (GO), having unique physicochemical properties, is widely used in various applications. GO prepared by a modified Hummer's method was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and BET surface area analysis. The adsorption properties of the prepared GO towards Co(II) was elucidated by the batch adsorption method, indicating the maximum adsorption of Co(II) in a broad pH range of 5.0 to 8.0. The batch adsorption kinetics results suggest that the adsorption could be described as a rate-limiting pseudosecond-order process. To the adsorption equilibrium data applied the Langmuir, Freundlich and Temkin adsorption isotherm models for an evaluation of adsorption capacity and relevant mechanism. These results revealed that the adsorption was occurring through physical and chemical interactions between Co(II) and oxygencontaining surface functional groups, –C–O and –C_O, and the π–π bonds electrons (–C_C–, –C_O) of GO. XPS (binding energy and shape of O1s and C1s) analysis of the GO material confirmed loading with Co(II). The maximum adsorption capacity was 21.28 mg/g of Co(II) at pH 5.5 and 298 K with 1.0 g/L GO, comparable to the reported adsorbents. Moreover, GO was precipitated upon loading with metal ions. Finally, the obtained results demonstrated the potential of the GO solid adsorbent for pre-concentration of trace heavy metals from waste effluents. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Cobalt is an essential element present in various salts in certain ores of the earth's crust. Pure cobalt is an odorless, steely-gray, hard and heavy metal which is widely used in the preparation of semiconductors, and in nuclear medicine, enamel and painting on glass, grinding wheels, porcelain, hydrometers, electroplating, aerospace materials and alloys manufacturing (Koduru et al., 2013; Rengaraj and Moon, 2002). Due to the increasing demand for cobalt, in the current and future in a wide area of applications and a variety of industries (especially in rechargeable batteries), cobalt metal recovery from its resources is necessary (Ahmadi et al., 2015; Srivastava et al., 2014; US Dept. of Energy report on Critical Materials Strategy, 2010; Zhang et al., 2012). Moreover, the increasing level of cobalt in the environment has created several health risks, such as low blood pressure, lung irritation, paralysis, diarrhea, and bone defects, and may also cause genetic changes in living cells (Lingamdinne et al., 2015a; Zhang et al., 2011). Precipitation, reverse osmosis, co-precipitation, ion-exchange, membrane, electrolysis, oxidation and adsorption methods are regularly used for removal of ⁎ Corresponding authors. E-mail addresses: [email protected] (J.R. Koduru), [email protected] (Y.-Y. Chang), [email protected] (J.-K. Yang).
Co(II) ions from aqueous solutions (Ahmadpour et al., 2009; Dell'Era et al., 2014; Gupta et al., 2003; Krause and Sandenbergh, 2015; Mizera et al., 2007; Oliva et al., 2011). However, at low concentrations, the removal of such pollutants is more effectively implemented by ion exchange or adsorption on a solid sorbent such as activated carbon (Nelson et al., 1974; Sigworth and Smith, 1972) or coal fly ash (Prabhu et al., 1981; Sen and De, 1987). Moreover, adsorption is one of the most effective methods for removal of heavy metals due to unique advantages such as the ease of experimental handling and the wide availability of various adsorbents at low prices. However, problems exist with filtration, centrifugation or gravitational separation of adsorbent from aqueous solutions, and an alternative effective adsorbents need to be developed. Graphene has a unique atom-thick two-dimensional (2D) structure and excellent mechanical, thermal and electrical properties (Murat et al., 1997). Graphene oxide (GO), an oxygen-rich carbonaceous layered material, is obtained by the oxidation of graphite. GO has an extended layered structure with hydrophilic polar groups, such as –OH, –COOH, and epoxy groups which can be procured from its layers. It also has, interesting swelling, intercalating and ion exchange properties (Geim, 2009; Posa et al., 2015). It has also been used for bacterial eradication (Akhavan and Ghaderi, 2010; Das et al., 2011; Hu et al., 2010; Park et al., 2010). The most popular method employed for
http://dx.doi.org/10.1016/j.hydromet.2015.10.021 0304-386X/© 2015 Elsevier B.V. All rights reserved.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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the synthesis of GO is the chemical oxidation of graphite (Dreyer et al., 2010). The advantage of this method is the formation large quantity of few layered graphene oxide which is dispersible in both polar and non-polar solvents by functionalization on the surface of graphene (Dreyer et al., 2010; Gao et al., 2010; Huang et al., 2011). This method imparts in the GO a favorable high adsorption capacity for heavy metals from a large amount of aqueous solution. The adsorption of metal ions on GO can overcome the aforementioned issues associated with filtration, centrifugation or the gravitational separation of adsorbents from aqueous solutions (Sitko et al., 2013). In the present study, GO was prepared by chemical oxidation using strong oxidizing agents (H2SO4 and KMnO4) by a slight modification of the popular Hummer's method (Hummers and Offeman, 1958). The physical and chemical characteristics of GO were identified by spectral characterization using XRD, FT-IR, XPS, SEM and BET analyses. Then, the adsorption properties of the prepared GO towards Co(II) were elucidated by a batch adsorption method. 2. Materials and methods 2.1. Materials All chemicals used in this work were of analytical grade, unless otherwise stated. Graphite flake powder was supplied by Sigma Aldrich (USA). H2SO4 (98%), CoCl2·6H2O, HCl (40%), and NH4OH (56.6%) were supplied by the Samchun Pure Chemicals Co. Ltd. (Korea). KMnO4 and NaOH (98%) were supplied by Kanto Chemical Co. Inc. (Japan). NaNO3 (98%) was supplied by Duksan Pure Chemicals (Korea). H2O2 (30%) was supplied by Junsei Chemicals Co. Ltd. (Japan). 2.2. Synthesis of the graphene oxide (GO) GO was prepared using a slightly modified Hummers method (Hummers and Offeman, 1958) through chemical oxidation of graphite flake powder. In this method, 1.0 g of graphite flake powder was added to concentrated H2SO4 (25 mL, 98%) in a 500 mL round-bottom flask under vigorous stirring in an ice bath at b5 °C. While maintaining vigorous stirring, 1.5 g of NaNO3 was added and stirred for 10 min. To this solution, an oxidizing agent (6.0 g KMnO4) was added and stirred for 30 min at an ice bath temperature (b5 °C) until it became a pasty brownish color. The reaction flask was then removed from the ice bath and stirred at room temperature for 3 h. After 3 h of stirring the reaction solution, 50 mL of double-distilled de-ionized water was added. With this addition, the temperature of the reaction solution was held at room temperature with stirring overnight. After overnight stirring, the reaction solution was diluted with 250 mL of double-distilled deionized water. Then, 7 mL of 30% H2O2 was added to stop the reaction, where the color of the mixture changed to bright yellow. It was filtered and washed with a 1:10 HCl solution several times to remove the residual metal ions. The pH of final product was then adjusted to a neutral pH using 30% NH3 solution. After neutralization, the end product was treated with ultrasonication for 30 min, centrifuged and dried at room temperature under vacuum condition. 2.3. Characterization of the prepared GO The crystalline characteristics and formation of the prepared GO were primarily confirmed by XRD analysis using Rigaku D/Max-2500 X-ray diffracto-meter (Japan). Further, functional groups of GO were identified by a FT-IR analysis using a Spectrum GX & Auto image FT-IR (Perkin-Elmer, USA). An ESCALAB-210 (Spain) X-ray photoelectron spectroscopy (XPS) was used for an elemental analysis of the prepared samples. A Mastersizer-3000 (UK) particle size analyzer was used to measure the size of the GO. An S-4300 SEM equipped with an EDX-350 unit (Hitachi, Japan) was used for measuring surface morphology and composition. An Autosorb-1 analyzer (Quanta-chrome
Instruments, USA) was used to measure the surface area and pore sizes of the GO. A Sonics Vibracell (CV 334, USA) was used for the ultrasonication of the GO. 2.4. Batch adsorption characteristics of GO The adsorption characteristics of GO towards Co(II) were studied by the batch adsorption technique in the polyethylene falcon tube under ambient conditions. Standard solution of Co(II) was made by the dilution of stock solution (1000 mg/L of Co(II)), prepared from CoCl2·6H2O. Batch adsorption experiments were carried out with a shaking rotator loaded with a Falcon tube containing 1.0 g/L GO in 40 mL of Co(II) (2–25 mg/L) at pH 5.5 and room temperature for a pre-determined equilibrium time (60 min). At the end of the equilibrium time, the filtrate of each sample was collected through a 0.45 μm membrane syringe filter. The residual metal ion concentration was measured using inductively coupled plasma emission spectroscopy (ICP-OES) (Optima 2100 DV, Perkin-Elmer, USA). The amount of metal ion adsorbed onto the GO was calculated from the mass balance between the initial (Co) and equilibrium (Ce) concentrations (mg/L) of the metal ions. The metal uptake capacity of GO (qe, mg/g), adsorption percentage (% adsorption) and adsorption capacity at time, t (qt, mg/g) were calcuC o −C f Co Þ
e ÞV lated by the following equations: qe ¼ ðC o −C , % adsorption = ð m
ðC o −C t ÞV , m
respectively. Where V is the solution volume, 100 and qt ¼ m (g) is the weight of the GO and Cf is the final metal ion concentration (mg/L). Each experiment was carried out in triplicate to avoid any discrepancies in the measured results. The pH measurements were carried out using a pH meter (340i, WTW, Germany). The adsorption experiment was also performed at different pH values by adjusting the pH with equimolar solutions of HCl and NaOH. 2.5. Statistical analysis All the investigations were carried out in triplicate to avoid discrepancies in experimental results, and the values reported are the mean ± standard deviation (SD). Origin 8.0© was used to fit the kinetics and equilibrium models using a linear regression analysis. 3. Results and discussion 3.1. Characterization of the prepared GO XRD analysis was performed to confirm the crystalline properties and the primary formation of GO (Fig. 1). The prepared GO showed a strong peak at 2θ_11.3°, indicating the formation of crystalline GO (Fan et al., 2010; Marcano et al., 2010; Song et al., 2014). The results of FT-IR analysis also identified the formation of GO (Fig. 1). After the oxidation of graphite to graphene oxide, various functional groups were observed on the GO (Marcano et al., 2010; Song et al., 2014). The sharp peaks at 412–1500 cm− 1 indicate the symmetric –C–C_C– stretching vibrations at aromatic alkenes or H–C–H bending vibrations in the alkanes of the aromatic ring. The peaks at 1200–1000 cm−1 indicate the –C–O stretching vibrations of epoxy and alkoxy groups in ester or ethers. The sharp peak at 1730 cm−1 indicates the –C_O stretching vibration in carboxylic acids and the broad peaks around 3017 to 3173 cm− 1 are assigned to hydrogen bond –OH groups on aromatic alcohol or carboxylic acids. Further XPS (Fig. 1) studies of graphite and GO found a difference in the intensity of the binding energies or the shapes of the C (1 s) and O (1 s) peaks of GO from graphite; high intensity of O (1 s) and low intensity of C (1 s) were found after the oxidation of graphite to GO. The SEM image of GO (Fig. 1) shows a rough surface, which is favorable for adsorption. The overall characterization results confirmed the formation of a micro crystalline rough surface morphology on GO. The BET surface area of GO was 2.8 m2/g with an average
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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Fig. 1. Characterization studies of the prepared GO using XRD, FT-IR (insets indicate graphite FT-IR), SEM and XPS (along with graphite) techniques.
micro pore volume of 0.01 cm3/g and a pore diameter of 14.34 nm, indicating the crystalline mesoporous nature of GO. 3.2. Adsorption characteristics of GO 3.2.1. Effect of the pH, dosage and ionic strength on the adsorption of Co(II) onto GO Effect of the pH on the adsorption of Co(II) with GO (Fig. 2a1) demonstrated that the adsorption percentage of Co(II) onto GO increased with an increase in the pH from 2.0–5.0 and remained constant at pH 5.0–8.0, where cobalt species as in Co(II) (N90%) (Sitko et al., 2013). This trend is explained by the competitive adsorption between aqueous H+ ions and metal ions on the surface-active sites of GO at a lower pH. However, favorable adsorption was observed with increasing pH and
moreover, the point of zero-charge pH (pHpzc) value of GO is 3.8 to 3.9 (Sitko et al., 2013). Therefore, at pH N 4.0, the surface charge of GO is negative charged and causes strong electrostatic interaction between metal ion and GO. At higher pH (N7.0), Co(II) precipitates as hydrated complexes in aqueous solutions. Therefore, examinations were not done at higher aqueous solution pH levels. Moreover, the adsorption capacity was constant from pH 5.0 to 6.0, hence; further studies were carried out at pH 5.5. In Fig. 2a2 observed the adsorption percentage increases as the GO dosage increases from 0.0 to 1.0 g/L and is held constant above 1.0 g/L. However, the Co(II) adsorption capacity (q) for a unit area of GO mass decreases with an increase in the dosage, possibly due to the decreased number of available active sites owing to the interchelating of GO molecules as the dosage increases. These results suggest that a 1.0 g/L GO dosage is required for the maximum adsorption of
Fig. 2. Effects of the pH (a1) and GO dosage (a2) on the adsorption of Co(II)(15 mg/L) onto GO(1.0 g/L for pH studies) at pH 5.5 and a temperature of 298 ± 2 K.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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Fig. 3. Effect of the contact time (b1) and associated pseudo-first-order (b2) and second-order (b3) kinetic models of the Co(II) adsorption onto GO(1.0 g/L) at pH 5.5 and a 298 ± 2 K temperature.
Table 1 Kinetic parameters of the Co(II) adsorption onto GO (n = 3, mean ± SD). Initial Co(II) concentration (mg/L)
qexp. (mg/g) e,
15.0 25.0
14.40 ± 0.012 19.23 ± 0.011
Pseudo-first-order
Pseudo-second-order
qcal. e, (mg/g)
K1 (min−1)
R2
qcal. (mg/g) e
K2 (g/mg min)
R2
0.14 ± 0.020 0.47 ± 0.030
0.02 ± 0.005 0.03 ± 0.004
0.703 0.744
14.49 ± 0.012 19.26 ± 0.011
2.38 ± 0.002 0.45 ± 0.001
0.999 0.999
Co(II). The effect of the ionic strength on the adsorption of Co(II) onto GO was studied using NaCl and KCl (0.005 to 0.05 mol/L) solutions. The obtained results found to be a weak dependence of the adsorption of desired metal ions onto GO with ionic strength. 3.2.2. Contact time and adsorption kinetic studies of the Co(II) adsorption onto GO Fig. 3b1 shows the adsorption of Co(II) onto GO to be rapid, exceeding 93% of Co(II) (93.8% at 5 min) within 5 min, and then reaching an equilibrium at 60 min. However, at a fixed adsorbent dosage, the
removal percentage of Co(II) decreases with an increasing initial metal ion concentration due to the lack of available active sites on the adsorbent as the initial metal ion concentration increases. In subsequent experiments, 60 min was selected to ascertain the adsorption equilibrium of Co(II) onto GO. To analyze the adsorption kinetic rate constant of Co(II) adsorption onto GO, pseudo-first-order and pseudo-secondorder kinetics models were applied to the experimental data. The suitability of the models was evaluated in terms of the correlation coefficient (R2), the difference in the metal up take capacity of adsorbent (qe) as calculated by theoretical and experimental means, and the
Fig. 4. Isotherm studies of the Co(II) (15 mg/L) adsorption onto GO (1.0 g/L) (c1) and associated Freundlich (c2) isotherm models at pH 5.5 and a 298 ± 2 K temperature.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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Table 2 Isotherm parameters of the Co(II) adsorption onto GO (n = 3, mean ± SD). Langmuir
Freundlich
Temkin
qmax. (mg/g)
KL, (L/mg)
R2
RL
KF (mg/g (Lmg−1)1/n)
n
R2
KT (L/mg)
B
R2
21.28 ± 0.022
0.783 ± 0.021
0.962
0.078 ± 0.002
8.30 ± 0.012
2.43 ± 0.002
0.991
24.30 ± 0.032
7.51 ± 0.025
0.897
standard deviation of the measurements. The linear pseudo- firstorder and second-order kinetic models can be expressed as logðqe −qt Þ ¼ K1 Þt and t =qt ¼ ð1 K q2 Þ þ ð1 q Þt , respectively, where K1 logðqe Þ−ð2:303 2 e
e
(min−1) and K2(g/mg . min) are the first-order and second-order rate constants obtained from the respective linear curve slopes (Fig. 3b2 & b3). The kinetics parameters are summarized in Table 1. The high correlation coefficient (R2) with a lower standard deviation and the low difference of adsorption capacity values obtained from the derivation (qcal. e ) and the experiment (qexp. e ) (Table 1) suggested the pseudo-second-order kinetics can be tuned with the experimental adsorption data. However, the pseudo-first-order only works effectively in regions where the adsorption process is rapid. From these obtained results, it can be concluded that the adsorption of Co(II) onto GO was the rate-controlling step in the pseudo-second-order kinetics.
3.2.3. Evaluation of the Co(II) adsorption isotherms characteristics As shown in Fig. 4c1, the metal uptake capacity to increase with increasing equilibrium concentration from 2.0–25.0 mg/L. To evaluate the adsorption mechanism and capacity, the Langmuir, Freundlich, and Temkin isotherm models were applied to equilibrium data obtained at 298 ± 2 K (Fig. 4c1). The correlation coefficient (R2) values expressed the suitability of the isotherm. The linear Langmuir (Eq. (1)), Freundlich (Eq. (2)) and Temkin (Eq. (3)) isotherm models can be expressed as follows: Ce 1 1 Ce ¼ þ b qe b 1 KL
ð1Þ
logqe ¼ lo g K f þ ð1=nÞ logC e
ð2Þ
Fig. 5. FT-IR, SEM, XPS results of the Co(II)-loaded GO for explanation of adsorption mechanism.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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qe ¼ B logK T þ B logC e :
ð3Þ
Here the constants, b, KL, and 1/n, KF and B, and BlogKT were calculated from the slope and intercept of the linear curves of Ce/qe vs Ce (Fig. S: see supplementary materials), logCe vs logqe (Fig. 4c2) and qe vs logCe (Fig. S), respectively; the resulting isotherm parameters are summarized in Table 2. The obtained correlation coefficient (R2) values suggest the Freundlich isotherm model as the best fit to the experimental equilibrium data. The other two models did not fit the equilibrium data well. The calculated value of n was 2.42 (N1), indicating multilayer adsorption onto the heterogeneous surface. 3.2.4. Evaluation of the Co(II) adsorption mechanism onto GO The FT-IR spectrum analysis of the Co(II)-loaded GO (Fig. 5) was used to explain the adsorption mechanism. Shifts of the absorption peaks were clearly observed, i.e., –C–O (1045–1037 cm− 1), –C_O (1730–1712 cm−1 and –C_C–C (1560–1564 cm−1) upon the adsorption of Co(II) onto GO. These absorption peak shifts assigned the loading of Co(II) onto GO. Further, this was also confirmed from the XPS spectrum of Co(II)-loaded GO compared with the bare GO (Fig. 5). The shifting of the binding energy of O (1 s) to a higher range was clearly observed upon loading with Co(II) onto GO, stemming from the binding or interaction between the oxygen-containing carbonyl or hydroxyl groups of GO and the metal ions. A SEM analysis (Fig. 5) showed the different surface morphologies of the GO and the metal-loaded GO (GO-Co(II)). The difference in the surface morphology of GO and GOCo(II) indicates the adsorption of Co(II) onto GO. These overall results demonstrate that the adsorption of Co(II) onto GO occurs through weak Van der Waals forces or by means of electrostatic physical interaction between the metal ions and oxygen-containing –C–O and –C_O or –C_C (π–π bond electrons) surface functional groups of GO. However, the adsorption of Co(II) was weak dependent on the ionic strength as well as great adsorption fraction of Co(II) onto GO below point of zero-charge pH (pHpzc) (3.8–3.9) suggests chemisorption. In conclusion, the adsorption of Co(II) onto GO was complexed by physical and chemical interactions. 3.3. Thermodynamic studies of the Co(II) adsorption onto GO The interactions the between adsorbent and the solute as well as the resulting energy changes in the adsorption process are explained by the thermodynamics parameter, the Gibb's free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°), determined using the following equations: ΔGo ¼ −RT LogK c
ð4Þ
ΔGo ¼ ΔHo −TΔSo
ð5Þ
Table 3 Thermodynamic parameters of the Co(II) (25 mg/L) adsorption onto GO (1.0 g/L) at pH 5.5 for 120 min (n = 3, mean ± SD). Temperature (K)
Log Kc (L/g)
ΔGo = −RTLogKc (kJ/mol)
ΔH° (kJ/mol)
ΔS° (kJ/mol·K)
293 308 323
0.425 ± 0.001 0.431 ± 0.001 0.447 ± 0.001
−1.035 ± 0.001 −1.105 ± 0.002 −1.201 ± 0.001
0.588 ± 0.001
0.005 ± 0.001
where R is the universal gas constant (8.314 × 10−3 k J mol/K), T (K) is the temperature of the system, Kc is the equilibrium constant describing from the ratio of the maximum metal uptake by the adsorbent (qe) and the equilibrium concentration(Ce) at adsorption equilibrium. The slope and intercept of a linear plot drawn between ΔG° vs T (Fig. 6) denote the ΔS° and ΔH° values, respectively, and are summarized in Table 3. The obtained negative ΔG° indicates that the free energy is spontaneous, and the positive ΔH° indicates that the activation energy is endothermic at the equilibrium surface. The positive values of the entropy (ΔS°) indicate that the adsorption of Co(II) onto GO was random, signifying a significant disruption during the activation stage in the range of 293–323 K (Koduru et al., 2013; Tahir and Rauf, 2003). The positive ΔS° suggests that the randomness on the surface of the adsorbent caused by structural changes or hydration disruption at the solid–liquid interface in the adsorption system increase the adsorption as the temperature increases. Moreover, the positive values of ΔH° and ΔS° also suggest that the adsorption was occurred by an inner sphere complex (Kislik, 2012; Lingamdinne et al., 2015b; Srivastava et al., 2013, 2015). 4. Conclusions XRD, FT-IR, and XPS analyses were confirmed the formations of crystalline and functionalized mesoporous GO. SEM and BET analyses of the GO indicated that the surface morphology and surface area of GO can be useful for the adsorption of target adsorbates. The results of FT-IR, XPS, and SEM morphology of Co(II) loaded GO concluded that the adsorption of Co(II) onto GO occurred through oxygen-containing –C–O and –C_O or –C_C (π–π bond electrons) surface functional groups of GO. The adsorption characteristics of the GO were well elucidated by batch adsorption of Co(II) from an aqueous solutions. These results demonstrate Co(II) adsorption onto GO via a multilayer adsorption on the heterogeneous surface functional groups involving physical and chemical interactions with metal ions (complexed), and was well described by rate-limiting pseudo-second-order kinetics. The thermodynamic results concluded that the adsorption of Co(II) onto GO was spontaneous endothermic with positive entropy at activated adsorption equilibrium stage. Acknowledgment This work was supported by the Korean Ministry of the Environment as part of the “GAIA project (2014000550003)” with additional support from the “Research Grant–2015” of Kwangwoon University, Seoul, Korea. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.hydromet.2015.10.021. References
Fig. 6. Thermodynamic studies of the Co(II) (25 mg/L) adsorption onto GO (1.0 g/L) at pH 5.5 for 120 min in the temperature range of 293–323 K.
Ahmadi, A., Khezri, M., Abdollahzadeh, A.A., Askari, M., 2015. Bioleaching of copper, nickel and cobalt from the low grade sulfidic tailing of Golgohar Iron Mine, Iran. Hydrometallurgy 154, 1–8. Ahmadpour, A., Tahmasbi, M., Rohani Bastami, T., Amel Besharati, J., 2009. Rapidremoval of cobalt ion from aqueous solutions by almond green hull. J. Hazard. Mater. 166, 925–930.
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L.P. Lingamdinne et al. / Hydrometallurgy xxx (2015) xxx–xxx Akhavan, O., Ghaderi, E., 2010. Toxicity of graphene and graphene oxide nanowalls against bacteria. ACS Nano 4, 5731–5736. Das, M.R., Sarma, R.K., Saikia, R., Kale, V.S., Shelke, M.V., Sengupta, P., 2011. Synthesis of silver nanoparticles in an aqueous suspension of graphene oxide sheets and its antimicrobial activity. Colloids Surf. B: Biointerfaces 83, 16–22. Dell'Era, A., Pasquali, M., Lupi, C., Zaza, F., 2014. Purification of nickel or cobalt ion containing effluents by electrolysis on reticulated vitreous carbon cathode. Hydrometallurgy 150, 1–8. Dreyer, D.R., Park, S., Bielawski, C.W., Ruoff, R.S., 2010. The chemistry of graphene oxide. Chem. Soc. Rev. 39, 228–2240. Fan, Z.J., Wang, K., Wei, T., Yan, J., Song, L.P., Shao, B., 2010. An environmentally friendly and efficient route for the reduction of graphene oxide by aluminum powder. Carbon 48 (5), 1670–1692. Gao, J., Liu, F., Liu, Y., Ma, N., Wang, Z., Zhang, X., 2010. Environment-friendly method to produce graphene that employs vitamin C and amino acid. Chem. Mater. 22, 2213–2218. Geim, A.K., 2009. Graphene: status and prospects. Science 324, 1530–1534. Gupta, V.K., Jain, C.K., Ali, I., Sharma, M., Saini, V.K., 2003. Removal of cadmium and nickel from wastewater using bagasse fly ash—a sugar industry waste. Water Res. 37, 4038–4044. Hu, W., Peng, C., Luo, W., et al., 2010. Graphene-based antibacterial paper. ACS Nano 4, 4317–4323. Huang, N.M., Lim, H.N., Chia, C.H., Yarmo, M.A., Muhamad, M.R., 2011. Simple roomtemperature preparation of high-yield large-area graphene oxide. Int. J. Nanomedicine 6, 3443–3448. Hummers Jr., S.W., Offeman, R.E., 1958. Preparation of graphitic oxide. J. Am. Chem. Soc. 80 (6), 1339. Kislik, V.S., 2012. Solvent Extraction: Classical and Novel Approaches. 1st edn. Elsevier, Amsterdam. Koduru, J.R., Chang, Y.Y., Yang, J.K., Kim, I.S., 2013. Iron oxide impregnated Morus alba L. fruit peel for biosorption of Co(II): biosorption properties and mechanism. Sci. World J. 2013, 917146. http://dx.doi.org/10.1155/2013/917146 (14 pp.). Krause, B., Sandenbergh, R.F., 2015. Optimization of cobalt removal from an aqueous sulfate zinc leach solution for zinc electrowinning. Hydrometallurgy 155, 132–140. Lingamdinne, L.P., Koduru, J.R., Jyothi, R.K., Chang, Y.-Y., Yang, J.-K., 2015a. Factors affect on bioremediation of Co(II) and Pb(II) onto Lonicera japonica flowers powder. Desalin. Water Treat. http://dx.doi.org/10.1080/19443994.2015.1055813. Lingamdinne, L.P., Roh, H., Choi, Y.-L., Koduru, J.R., Yang, J.-K., Chang, Y.-Y., 2015b. Influencing factors on sorption of TNT and RDX using rice husk biochar. J. Ind. Eng. Chem.http://dx.doi.org/10.1016/j.jiec.2015.08.012 Marcano, D.C., Kosynkin, D.V., Berlin, J.M., Sinitskii, A., Sun, Z., Slesarev, A., Alemany, L.B., Lu, W., Tour, J.M., 2010. Improved synthesis of graphene oxide. ACS Nano 4 (8), 4806–4814. Mizera, J., Mizerova, G., Machovic, V., Borecka, L., 2007. Sorption of cesium, cobalt and europium on low-rank coal and chitosan. Water Res. 41, 620–626.
7
Murat, T., Omer, S., Mustafa, I., 1997. Adsorption of cobalt by activated carbon from the rice hulls. J. Environ. Sci. Health 32, 2077–2086. Nelson, F., Phillips, H.O., Kraus, K.A., 1974. Adsorption of inorganic materials on activated carbon. Eng. Bull. Ext. Ser. 145, 1076–1090. Oliva, J., Pablo, J.D., Cortina, J.-L., Cama, J., Ayora, C., 2011. Removal of cadmium, copper, nickel, cobalt and mercury from water by Apatite IITM: column experiments. J. Hazard. Mater. 194, 312–323. Park, S., Mohanty, N., Suk, J.W., Nagaraja, A., An, J., Piner, R.D., Cai, W., Dreyer, D.R., Berry, V., Ruoff, R.S., 2010. Biocompatible, robust free-standing paper composed of a TWEEN/graphene composite. Adv. Mater. 22, 1736–1740. Posa, V.R., Annavaram, V., Koduru, J.R., Ammireddy, V.R., Somala, A.R., 2015. GrapheneZnO nanocomposite for highly efficient photocatalytic degradation of methyl orange dye under solar light irradiation. Korean J. Chem. Eng. 2015. http://dx.doi.org/10. 1007/s11814-015-0145-4 (Online). Prabhu, P.V.S.S., Narayana Swamy, M.S., Narasa Raju, T.S.S., 1981. Adsorption of zinc from aqueous solutions by fly ash. IAWPC Technical Annual report 8, pp. 46–52. Rengaraj, S., Moon, S.-H., 2002. Kinetics of adsorption of Co(II) removal from water and wastewater by ion exchange resins. Water Res. 36, 1783–1793. Sen, A.K., De, A.K., 1987. Adsorption of mercury(II) by coal fly ash. Water Res. 21, 885–888. Sigworth, E.A., Smith, S.B., 1972. Adsorption of inorganic compounds by activated carbon. J. Am. Water Works Assoc. 64, 386–391. Sitko, R., Turek, E., Zawisza, B., Malicka, E., Talik, E., Heimann, J., Gagor, A., Feist, B., Wrzalik, R., 2013. Adsorption of divalent metal ions from aqueous solutions using graphene oxide. Dalton Trans. 42, 5682–5689. Song, J., Wang, X., Chang, C.-T., 2014. Preparation and characterization of graphene oxide. J. Nanomater. 2014, 276143 (6 pp.). Srivastava, R.R., Kim, M.-S., Lee, J.-C., 2013. Separation of tungsten from Mo-rich leach liquor by adsorption onto a typical Fe–Mn cake: kinetics, equilibrium, mechanism, and thermodynamics studies. Ind. Eng. Chem. Res. 2013 (52), 17591–17597. Srivastava, R.R., Kim, M.-S., Lee, J.-C., Jha, M.K., Kim, B.-S., 2014. Resource recycling of superalloys and hydrometallurgical challenges. J. Mater. Sci. 49 (14), 4671–4686. Srivastava, R.R., Lee, J.-C., Kim, M.-S., 2015. Complexation chemistry in liquid–liquid extraction of rhenium. J. Chem. Technol. Biotechnol. 2015. http://dx.doi.org/10. 1002/jctb.4707. Tahir, S.S., Rauf, N., 2003. Thermodynamic studies of Ni(II) adsorption onto bentonite from aqueous solution. J. Chem. Thermodyn. 35 (12), 2003–2009. US Dept. of Energy report on Critical Materials Strategy, 2010. (December). Zhang, S., Guo, Z., Xu, J., Niu, H., Chen, Z., Xu, J., 2011. Effect of environmental conditions on the sorption of radiocobalt from aqueous solution to treated eggshell as biosorbent. J. Radioanal. Nucl. Chem. 288 (1), 121–130. Zhang, M., Zhu, G., Zhao, Y., Feng, X., 2012. A study of recovery of copper and cobalt from copper–cobalt oxide ores by ammonium salt roasting. Hydrometallurgy 129–130, 140–144.
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Adsorption removal of Co(II) from waste-water using graphene oxide Lakshmi Prasanna Lingamdinne a, Janardhan Reddy Koduru b,⁎, Hoon Roh a, Yu-Lim Choi a, Yoon-Young Chang a,⁎, Jae-Kyu Yang c,⁎ a b c
Department of Environmental Engineering, Kwangwoon University, Seoul 139-701, Republic of Korea Graduate School of Environmental Studies, Kwangwoon University, Seoul 139-701, Republic of Korea Division of General Education, Kwangwoon University, Seoul 139-701, Republic of Korea
a r t i c l e
i n f o
Article history: Received 22 May 2015 Received in revised form 19 October 2015 Accepted 23 October 2015 Available online xxxx Keywords: Adsorption Graphene oxide Co(II) removal Heavy metal XRD and XPS studies
a b s t r a c t Graphene oxide (GO), having unique physicochemical properties, is widely used in various applications. GO prepared by a modified Hummer's method was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and BET surface area analysis. The adsorption properties of the prepared GO towards Co(II) was elucidated by the batch adsorption method, indicating the maximum adsorption of Co(II) in a broad pH range of 5.0 to 8.0. The batch adsorption kinetics results suggest that the adsorption could be described as a rate-limiting pseudosecond-order process. To the adsorption equilibrium data applied the Langmuir, Freundlich and Temkin adsorption isotherm models for an evaluation of adsorption capacity and relevant mechanism. These results revealed that the adsorption was occurring through physical and chemical interactions between Co(II) and oxygencontaining surface functional groups, –C–O and –C_O, and the π–π bonds electrons (–C_C–, –C_O) of GO. XPS (binding energy and shape of O1s and C1s) analysis of the GO material confirmed loading with Co(II). The maximum adsorption capacity was 21.28 mg/g of Co(II) at pH 5.5 and 298 K with 1.0 g/L GO, comparable to the reported adsorbents. Moreover, GO was precipitated upon loading with metal ions. Finally, the obtained results demonstrated the potential of the GO solid adsorbent for pre-concentration of trace heavy metals from waste effluents. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Cobalt is an essential element present in various salts in certain ores of the earth's crust. Pure cobalt is an odorless, steely-gray, hard and heavy metal which is widely used in the preparation of semiconductors, and in nuclear medicine, enamel and painting on glass, grinding wheels, porcelain, hydrometers, electroplating, aerospace materials and alloys manufacturing (Koduru et al., 2013; Rengaraj and Moon, 2002). Due to the increasing demand for cobalt, in the current and future in a wide area of applications and a variety of industries (especially in rechargeable batteries), cobalt metal recovery from its resources is necessary (Ahmadi et al., 2015; Srivastava et al., 2014; US Dept. of Energy report on Critical Materials Strategy, 2010; Zhang et al., 2012). Moreover, the increasing level of cobalt in the environment has created several health risks, such as low blood pressure, lung irritation, paralysis, diarrhea, and bone defects, and may also cause genetic changes in living cells (Lingamdinne et al., 2015a; Zhang et al., 2011). Precipitation, reverse osmosis, co-precipitation, ion-exchange, membrane, electrolysis, oxidation and adsorption methods are regularly used for removal of ⁎ Corresponding authors. E-mail addresses: [email protected] (J.R. Koduru), [email protected] (Y.-Y. Chang), [email protected] (J.-K. Yang).
Co(II) ions from aqueous solutions (Ahmadpour et al., 2009; Dell'Era et al., 2014; Gupta et al., 2003; Krause and Sandenbergh, 2015; Mizera et al., 2007; Oliva et al., 2011). However, at low concentrations, the removal of such pollutants is more effectively implemented by ion exchange or adsorption on a solid sorbent such as activated carbon (Nelson et al., 1974; Sigworth and Smith, 1972) or coal fly ash (Prabhu et al., 1981; Sen and De, 1987). Moreover, adsorption is one of the most effective methods for removal of heavy metals due to unique advantages such as the ease of experimental handling and the wide availability of various adsorbents at low prices. However, problems exist with filtration, centrifugation or gravitational separation of adsorbent from aqueous solutions, and an alternative effective adsorbents need to be developed. Graphene has a unique atom-thick two-dimensional (2D) structure and excellent mechanical, thermal and electrical properties (Murat et al., 1997). Graphene oxide (GO), an oxygen-rich carbonaceous layered material, is obtained by the oxidation of graphite. GO has an extended layered structure with hydrophilic polar groups, such as –OH, –COOH, and epoxy groups which can be procured from its layers. It also has, interesting swelling, intercalating and ion exchange properties (Geim, 2009; Posa et al., 2015). It has also been used for bacterial eradication (Akhavan and Ghaderi, 2010; Das et al., 2011; Hu et al., 2010; Park et al., 2010). The most popular method employed for
http://dx.doi.org/10.1016/j.hydromet.2015.10.021 0304-386X/© 2015 Elsevier B.V. All rights reserved.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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the synthesis of GO is the chemical oxidation of graphite (Dreyer et al., 2010). The advantage of this method is the formation large quantity of few layered graphene oxide which is dispersible in both polar and non-polar solvents by functionalization on the surface of graphene (Dreyer et al., 2010; Gao et al., 2010; Huang et al., 2011). This method imparts in the GO a favorable high adsorption capacity for heavy metals from a large amount of aqueous solution. The adsorption of metal ions on GO can overcome the aforementioned issues associated with filtration, centrifugation or the gravitational separation of adsorbents from aqueous solutions (Sitko et al., 2013). In the present study, GO was prepared by chemical oxidation using strong oxidizing agents (H2SO4 and KMnO4) by a slight modification of the popular Hummer's method (Hummers and Offeman, 1958). The physical and chemical characteristics of GO were identified by spectral characterization using XRD, FT-IR, XPS, SEM and BET analyses. Then, the adsorption properties of the prepared GO towards Co(II) were elucidated by a batch adsorption method. 2. Materials and methods 2.1. Materials All chemicals used in this work were of analytical grade, unless otherwise stated. Graphite flake powder was supplied by Sigma Aldrich (USA). H2SO4 (98%), CoCl2·6H2O, HCl (40%), and NH4OH (56.6%) were supplied by the Samchun Pure Chemicals Co. Ltd. (Korea). KMnO4 and NaOH (98%) were supplied by Kanto Chemical Co. Inc. (Japan). NaNO3 (98%) was supplied by Duksan Pure Chemicals (Korea). H2O2 (30%) was supplied by Junsei Chemicals Co. Ltd. (Japan). 2.2. Synthesis of the graphene oxide (GO) GO was prepared using a slightly modified Hummers method (Hummers and Offeman, 1958) through chemical oxidation of graphite flake powder. In this method, 1.0 g of graphite flake powder was added to concentrated H2SO4 (25 mL, 98%) in a 500 mL round-bottom flask under vigorous stirring in an ice bath at b5 °C. While maintaining vigorous stirring, 1.5 g of NaNO3 was added and stirred for 10 min. To this solution, an oxidizing agent (6.0 g KMnO4) was added and stirred for 30 min at an ice bath temperature (b5 °C) until it became a pasty brownish color. The reaction flask was then removed from the ice bath and stirred at room temperature for 3 h. After 3 h of stirring the reaction solution, 50 mL of double-distilled de-ionized water was added. With this addition, the temperature of the reaction solution was held at room temperature with stirring overnight. After overnight stirring, the reaction solution was diluted with 250 mL of double-distilled deionized water. Then, 7 mL of 30% H2O2 was added to stop the reaction, where the color of the mixture changed to bright yellow. It was filtered and washed with a 1:10 HCl solution several times to remove the residual metal ions. The pH of final product was then adjusted to a neutral pH using 30% NH3 solution. After neutralization, the end product was treated with ultrasonication for 30 min, centrifuged and dried at room temperature under vacuum condition. 2.3. Characterization of the prepared GO The crystalline characteristics and formation of the prepared GO were primarily confirmed by XRD analysis using Rigaku D/Max-2500 X-ray diffracto-meter (Japan). Further, functional groups of GO were identified by a FT-IR analysis using a Spectrum GX & Auto image FT-IR (Perkin-Elmer, USA). An ESCALAB-210 (Spain) X-ray photoelectron spectroscopy (XPS) was used for an elemental analysis of the prepared samples. A Mastersizer-3000 (UK) particle size analyzer was used to measure the size of the GO. An S-4300 SEM equipped with an EDX-350 unit (Hitachi, Japan) was used for measuring surface morphology and composition. An Autosorb-1 analyzer (Quanta-chrome
Instruments, USA) was used to measure the surface area and pore sizes of the GO. A Sonics Vibracell (CV 334, USA) was used for the ultrasonication of the GO. 2.4. Batch adsorption characteristics of GO The adsorption characteristics of GO towards Co(II) were studied by the batch adsorption technique in the polyethylene falcon tube under ambient conditions. Standard solution of Co(II) was made by the dilution of stock solution (1000 mg/L of Co(II)), prepared from CoCl2·6H2O. Batch adsorption experiments were carried out with a shaking rotator loaded with a Falcon tube containing 1.0 g/L GO in 40 mL of Co(II) (2–25 mg/L) at pH 5.5 and room temperature for a pre-determined equilibrium time (60 min). At the end of the equilibrium time, the filtrate of each sample was collected through a 0.45 μm membrane syringe filter. The residual metal ion concentration was measured using inductively coupled plasma emission spectroscopy (ICP-OES) (Optima 2100 DV, Perkin-Elmer, USA). The amount of metal ion adsorbed onto the GO was calculated from the mass balance between the initial (Co) and equilibrium (Ce) concentrations (mg/L) of the metal ions. The metal uptake capacity of GO (qe, mg/g), adsorption percentage (% adsorption) and adsorption capacity at time, t (qt, mg/g) were calcuC o −C f Co Þ
e ÞV lated by the following equations: qe ¼ ðC o −C , % adsorption = ð m
ðC o −C t ÞV , m
respectively. Where V is the solution volume, 100 and qt ¼ m (g) is the weight of the GO and Cf is the final metal ion concentration (mg/L). Each experiment was carried out in triplicate to avoid any discrepancies in the measured results. The pH measurements were carried out using a pH meter (340i, WTW, Germany). The adsorption experiment was also performed at different pH values by adjusting the pH with equimolar solutions of HCl and NaOH. 2.5. Statistical analysis All the investigations were carried out in triplicate to avoid discrepancies in experimental results, and the values reported are the mean ± standard deviation (SD). Origin 8.0© was used to fit the kinetics and equilibrium models using a linear regression analysis. 3. Results and discussion 3.1. Characterization of the prepared GO XRD analysis was performed to confirm the crystalline properties and the primary formation of GO (Fig. 1). The prepared GO showed a strong peak at 2θ_11.3°, indicating the formation of crystalline GO (Fan et al., 2010; Marcano et al., 2010; Song et al., 2014). The results of FT-IR analysis also identified the formation of GO (Fig. 1). After the oxidation of graphite to graphene oxide, various functional groups were observed on the GO (Marcano et al., 2010; Song et al., 2014). The sharp peaks at 412–1500 cm− 1 indicate the symmetric –C–C_C– stretching vibrations at aromatic alkenes or H–C–H bending vibrations in the alkanes of the aromatic ring. The peaks at 1200–1000 cm−1 indicate the –C–O stretching vibrations of epoxy and alkoxy groups in ester or ethers. The sharp peak at 1730 cm−1 indicates the –C_O stretching vibration in carboxylic acids and the broad peaks around 3017 to 3173 cm− 1 are assigned to hydrogen bond –OH groups on aromatic alcohol or carboxylic acids. Further XPS (Fig. 1) studies of graphite and GO found a difference in the intensity of the binding energies or the shapes of the C (1 s) and O (1 s) peaks of GO from graphite; high intensity of O (1 s) and low intensity of C (1 s) were found after the oxidation of graphite to GO. The SEM image of GO (Fig. 1) shows a rough surface, which is favorable for adsorption. The overall characterization results confirmed the formation of a micro crystalline rough surface morphology on GO. The BET surface area of GO was 2.8 m2/g with an average
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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Fig. 1. Characterization studies of the prepared GO using XRD, FT-IR (insets indicate graphite FT-IR), SEM and XPS (along with graphite) techniques.
micro pore volume of 0.01 cm3/g and a pore diameter of 14.34 nm, indicating the crystalline mesoporous nature of GO. 3.2. Adsorption characteristics of GO 3.2.1. Effect of the pH, dosage and ionic strength on the adsorption of Co(II) onto GO Effect of the pH on the adsorption of Co(II) with GO (Fig. 2a1) demonstrated that the adsorption percentage of Co(II) onto GO increased with an increase in the pH from 2.0–5.0 and remained constant at pH 5.0–8.0, where cobalt species as in Co(II) (N90%) (Sitko et al., 2013). This trend is explained by the competitive adsorption between aqueous H+ ions and metal ions on the surface-active sites of GO at a lower pH. However, favorable adsorption was observed with increasing pH and
moreover, the point of zero-charge pH (pHpzc) value of GO is 3.8 to 3.9 (Sitko et al., 2013). Therefore, at pH N 4.0, the surface charge of GO is negative charged and causes strong electrostatic interaction between metal ion and GO. At higher pH (N7.0), Co(II) precipitates as hydrated complexes in aqueous solutions. Therefore, examinations were not done at higher aqueous solution pH levels. Moreover, the adsorption capacity was constant from pH 5.0 to 6.0, hence; further studies were carried out at pH 5.5. In Fig. 2a2 observed the adsorption percentage increases as the GO dosage increases from 0.0 to 1.0 g/L and is held constant above 1.0 g/L. However, the Co(II) adsorption capacity (q) for a unit area of GO mass decreases with an increase in the dosage, possibly due to the decreased number of available active sites owing to the interchelating of GO molecules as the dosage increases. These results suggest that a 1.0 g/L GO dosage is required for the maximum adsorption of
Fig. 2. Effects of the pH (a1) and GO dosage (a2) on the adsorption of Co(II)(15 mg/L) onto GO(1.0 g/L for pH studies) at pH 5.5 and a temperature of 298 ± 2 K.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
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Fig. 3. Effect of the contact time (b1) and associated pseudo-first-order (b2) and second-order (b3) kinetic models of the Co(II) adsorption onto GO(1.0 g/L) at pH 5.5 and a 298 ± 2 K temperature.
Table 1 Kinetic parameters of the Co(II) adsorption onto GO (n = 3, mean ± SD). Initial Co(II) concentration (mg/L)
qexp. (mg/g) e,
15.0 25.0
14.40 ± 0.012 19.23 ± 0.011
Pseudo-first-order
Pseudo-second-order
qcal. e, (mg/g)
K1 (min−1)
R2
qcal. (mg/g) e
K2 (g/mg min)
R2
0.14 ± 0.020 0.47 ± 0.030
0.02 ± 0.005 0.03 ± 0.004
0.703 0.744
14.49 ± 0.012 19.26 ± 0.011
2.38 ± 0.002 0.45 ± 0.001
0.999 0.999
Co(II). The effect of the ionic strength on the adsorption of Co(II) onto GO was studied using NaCl and KCl (0.005 to 0.05 mol/L) solutions. The obtained results found to be a weak dependence of the adsorption of desired metal ions onto GO with ionic strength. 3.2.2. Contact time and adsorption kinetic studies of the Co(II) adsorption onto GO Fig. 3b1 shows the adsorption of Co(II) onto GO to be rapid, exceeding 93% of Co(II) (93.8% at 5 min) within 5 min, and then reaching an equilibrium at 60 min. However, at a fixed adsorbent dosage, the
removal percentage of Co(II) decreases with an increasing initial metal ion concentration due to the lack of available active sites on the adsorbent as the initial metal ion concentration increases. In subsequent experiments, 60 min was selected to ascertain the adsorption equilibrium of Co(II) onto GO. To analyze the adsorption kinetic rate constant of Co(II) adsorption onto GO, pseudo-first-order and pseudo-secondorder kinetics models were applied to the experimental data. The suitability of the models was evaluated in terms of the correlation coefficient (R2), the difference in the metal up take capacity of adsorbent (qe) as calculated by theoretical and experimental means, and the
Fig. 4. Isotherm studies of the Co(II) (15 mg/L) adsorption onto GO (1.0 g/L) (c1) and associated Freundlich (c2) isotherm models at pH 5.5 and a 298 ± 2 K temperature.
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Table 2 Isotherm parameters of the Co(II) adsorption onto GO (n = 3, mean ± SD). Langmuir
Freundlich
Temkin
qmax. (mg/g)
KL, (L/mg)
R2
RL
KF (mg/g (Lmg−1)1/n)
n
R2
KT (L/mg)
B
R2
21.28 ± 0.022
0.783 ± 0.021
0.962
0.078 ± 0.002
8.30 ± 0.012
2.43 ± 0.002
0.991
24.30 ± 0.032
7.51 ± 0.025
0.897
standard deviation of the measurements. The linear pseudo- firstorder and second-order kinetic models can be expressed as logðqe −qt Þ ¼ K1 Þt and t =qt ¼ ð1 K q2 Þ þ ð1 q Þt , respectively, where K1 logðqe Þ−ð2:303 2 e
e
(min−1) and K2(g/mg . min) are the first-order and second-order rate constants obtained from the respective linear curve slopes (Fig. 3b2 & b3). The kinetics parameters are summarized in Table 1. The high correlation coefficient (R2) with a lower standard deviation and the low difference of adsorption capacity values obtained from the derivation (qcal. e ) and the experiment (qexp. e ) (Table 1) suggested the pseudo-second-order kinetics can be tuned with the experimental adsorption data. However, the pseudo-first-order only works effectively in regions where the adsorption process is rapid. From these obtained results, it can be concluded that the adsorption of Co(II) onto GO was the rate-controlling step in the pseudo-second-order kinetics.
3.2.3. Evaluation of the Co(II) adsorption isotherms characteristics As shown in Fig. 4c1, the metal uptake capacity to increase with increasing equilibrium concentration from 2.0–25.0 mg/L. To evaluate the adsorption mechanism and capacity, the Langmuir, Freundlich, and Temkin isotherm models were applied to equilibrium data obtained at 298 ± 2 K (Fig. 4c1). The correlation coefficient (R2) values expressed the suitability of the isotherm. The linear Langmuir (Eq. (1)), Freundlich (Eq. (2)) and Temkin (Eq. (3)) isotherm models can be expressed as follows: Ce 1 1 Ce ¼ þ b qe b 1 KL
ð1Þ
logqe ¼ lo g K f þ ð1=nÞ logC e
ð2Þ
Fig. 5. FT-IR, SEM, XPS results of the Co(II)-loaded GO for explanation of adsorption mechanism.
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qe ¼ B logK T þ B logC e :
ð3Þ
Here the constants, b, KL, and 1/n, KF and B, and BlogKT were calculated from the slope and intercept of the linear curves of Ce/qe vs Ce (Fig. S: see supplementary materials), logCe vs logqe (Fig. 4c2) and qe vs logCe (Fig. S), respectively; the resulting isotherm parameters are summarized in Table 2. The obtained correlation coefficient (R2) values suggest the Freundlich isotherm model as the best fit to the experimental equilibrium data. The other two models did not fit the equilibrium data well. The calculated value of n was 2.42 (N1), indicating multilayer adsorption onto the heterogeneous surface. 3.2.4. Evaluation of the Co(II) adsorption mechanism onto GO The FT-IR spectrum analysis of the Co(II)-loaded GO (Fig. 5) was used to explain the adsorption mechanism. Shifts of the absorption peaks were clearly observed, i.e., –C–O (1045–1037 cm− 1), –C_O (1730–1712 cm−1 and –C_C–C (1560–1564 cm−1) upon the adsorption of Co(II) onto GO. These absorption peak shifts assigned the loading of Co(II) onto GO. Further, this was also confirmed from the XPS spectrum of Co(II)-loaded GO compared with the bare GO (Fig. 5). The shifting of the binding energy of O (1 s) to a higher range was clearly observed upon loading with Co(II) onto GO, stemming from the binding or interaction between the oxygen-containing carbonyl or hydroxyl groups of GO and the metal ions. A SEM analysis (Fig. 5) showed the different surface morphologies of the GO and the metal-loaded GO (GO-Co(II)). The difference in the surface morphology of GO and GOCo(II) indicates the adsorption of Co(II) onto GO. These overall results demonstrate that the adsorption of Co(II) onto GO occurs through weak Van der Waals forces or by means of electrostatic physical interaction between the metal ions and oxygen-containing –C–O and –C_O or –C_C (π–π bond electrons) surface functional groups of GO. However, the adsorption of Co(II) was weak dependent on the ionic strength as well as great adsorption fraction of Co(II) onto GO below point of zero-charge pH (pHpzc) (3.8–3.9) suggests chemisorption. In conclusion, the adsorption of Co(II) onto GO was complexed by physical and chemical interactions. 3.3. Thermodynamic studies of the Co(II) adsorption onto GO The interactions the between adsorbent and the solute as well as the resulting energy changes in the adsorption process are explained by the thermodynamics parameter, the Gibb's free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°), determined using the following equations: ΔGo ¼ −RT LogK c
ð4Þ
ΔGo ¼ ΔHo −TΔSo
ð5Þ
Table 3 Thermodynamic parameters of the Co(II) (25 mg/L) adsorption onto GO (1.0 g/L) at pH 5.5 for 120 min (n = 3, mean ± SD). Temperature (K)
Log Kc (L/g)
ΔGo = −RTLogKc (kJ/mol)
ΔH° (kJ/mol)
ΔS° (kJ/mol·K)
293 308 323
0.425 ± 0.001 0.431 ± 0.001 0.447 ± 0.001
−1.035 ± 0.001 −1.105 ± 0.002 −1.201 ± 0.001
0.588 ± 0.001
0.005 ± 0.001
where R is the universal gas constant (8.314 × 10−3 k J mol/K), T (K) is the temperature of the system, Kc is the equilibrium constant describing from the ratio of the maximum metal uptake by the adsorbent (qe) and the equilibrium concentration(Ce) at adsorption equilibrium. The slope and intercept of a linear plot drawn between ΔG° vs T (Fig. 6) denote the ΔS° and ΔH° values, respectively, and are summarized in Table 3. The obtained negative ΔG° indicates that the free energy is spontaneous, and the positive ΔH° indicates that the activation energy is endothermic at the equilibrium surface. The positive values of the entropy (ΔS°) indicate that the adsorption of Co(II) onto GO was random, signifying a significant disruption during the activation stage in the range of 293–323 K (Koduru et al., 2013; Tahir and Rauf, 2003). The positive ΔS° suggests that the randomness on the surface of the adsorbent caused by structural changes or hydration disruption at the solid–liquid interface in the adsorption system increase the adsorption as the temperature increases. Moreover, the positive values of ΔH° and ΔS° also suggest that the adsorption was occurred by an inner sphere complex (Kislik, 2012; Lingamdinne et al., 2015b; Srivastava et al., 2013, 2015). 4. Conclusions XRD, FT-IR, and XPS analyses were confirmed the formations of crystalline and functionalized mesoporous GO. SEM and BET analyses of the GO indicated that the surface morphology and surface area of GO can be useful for the adsorption of target adsorbates. The results of FT-IR, XPS, and SEM morphology of Co(II) loaded GO concluded that the adsorption of Co(II) onto GO occurred through oxygen-containing –C–O and –C_O or –C_C (π–π bond electrons) surface functional groups of GO. The adsorption characteristics of the GO were well elucidated by batch adsorption of Co(II) from an aqueous solutions. These results demonstrate Co(II) adsorption onto GO via a multilayer adsorption on the heterogeneous surface functional groups involving physical and chemical interactions with metal ions (complexed), and was well described by rate-limiting pseudo-second-order kinetics. The thermodynamic results concluded that the adsorption of Co(II) onto GO was spontaneous endothermic with positive entropy at activated adsorption equilibrium stage. Acknowledgment This work was supported by the Korean Ministry of the Environment as part of the “GAIA project (2014000550003)” with additional support from the “Research Grant–2015” of Kwangwoon University, Seoul, Korea. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.hydromet.2015.10.021. References
Fig. 6. Thermodynamic studies of the Co(II) (25 mg/L) adsorption onto GO (1.0 g/L) at pH 5.5 for 120 min in the temperature range of 293–323 K.
Ahmadi, A., Khezri, M., Abdollahzadeh, A.A., Askari, M., 2015. Bioleaching of copper, nickel and cobalt from the low grade sulfidic tailing of Golgohar Iron Mine, Iran. Hydrometallurgy 154, 1–8. Ahmadpour, A., Tahmasbi, M., Rohani Bastami, T., Amel Besharati, J., 2009. Rapidremoval of cobalt ion from aqueous solutions by almond green hull. J. Hazard. Mater. 166, 925–930.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021
L.P. Lingamdinne et al. / Hydrometallurgy xxx (2015) xxx–xxx Akhavan, O., Ghaderi, E., 2010. Toxicity of graphene and graphene oxide nanowalls against bacteria. ACS Nano 4, 5731–5736. Das, M.R., Sarma, R.K., Saikia, R., Kale, V.S., Shelke, M.V., Sengupta, P., 2011. Synthesis of silver nanoparticles in an aqueous suspension of graphene oxide sheets and its antimicrobial activity. Colloids Surf. B: Biointerfaces 83, 16–22. Dell'Era, A., Pasquali, M., Lupi, C., Zaza, F., 2014. Purification of nickel or cobalt ion containing effluents by electrolysis on reticulated vitreous carbon cathode. Hydrometallurgy 150, 1–8. Dreyer, D.R., Park, S., Bielawski, C.W., Ruoff, R.S., 2010. The chemistry of graphene oxide. Chem. Soc. Rev. 39, 228–2240. Fan, Z.J., Wang, K., Wei, T., Yan, J., Song, L.P., Shao, B., 2010. An environmentally friendly and efficient route for the reduction of graphene oxide by aluminum powder. Carbon 48 (5), 1670–1692. Gao, J., Liu, F., Liu, Y., Ma, N., Wang, Z., Zhang, X., 2010. Environment-friendly method to produce graphene that employs vitamin C and amino acid. Chem. Mater. 22, 2213–2218. Geim, A.K., 2009. Graphene: status and prospects. Science 324, 1530–1534. Gupta, V.K., Jain, C.K., Ali, I., Sharma, M., Saini, V.K., 2003. Removal of cadmium and nickel from wastewater using bagasse fly ash—a sugar industry waste. Water Res. 37, 4038–4044. Hu, W., Peng, C., Luo, W., et al., 2010. Graphene-based antibacterial paper. ACS Nano 4, 4317–4323. Huang, N.M., Lim, H.N., Chia, C.H., Yarmo, M.A., Muhamad, M.R., 2011. Simple roomtemperature preparation of high-yield large-area graphene oxide. Int. J. Nanomedicine 6, 3443–3448. Hummers Jr., S.W., Offeman, R.E., 1958. Preparation of graphitic oxide. J. Am. Chem. Soc. 80 (6), 1339. Kislik, V.S., 2012. Solvent Extraction: Classical and Novel Approaches. 1st edn. Elsevier, Amsterdam. Koduru, J.R., Chang, Y.Y., Yang, J.K., Kim, I.S., 2013. Iron oxide impregnated Morus alba L. fruit peel for biosorption of Co(II): biosorption properties and mechanism. Sci. World J. 2013, 917146. http://dx.doi.org/10.1155/2013/917146 (14 pp.). Krause, B., Sandenbergh, R.F., 2015. Optimization of cobalt removal from an aqueous sulfate zinc leach solution for zinc electrowinning. Hydrometallurgy 155, 132–140. Lingamdinne, L.P., Koduru, J.R., Jyothi, R.K., Chang, Y.-Y., Yang, J.-K., 2015a. Factors affect on bioremediation of Co(II) and Pb(II) onto Lonicera japonica flowers powder. Desalin. Water Treat. http://dx.doi.org/10.1080/19443994.2015.1055813. Lingamdinne, L.P., Roh, H., Choi, Y.-L., Koduru, J.R., Yang, J.-K., Chang, Y.-Y., 2015b. Influencing factors on sorption of TNT and RDX using rice husk biochar. J. Ind. Eng. Chem.http://dx.doi.org/10.1016/j.jiec.2015.08.012 Marcano, D.C., Kosynkin, D.V., Berlin, J.M., Sinitskii, A., Sun, Z., Slesarev, A., Alemany, L.B., Lu, W., Tour, J.M., 2010. Improved synthesis of graphene oxide. ACS Nano 4 (8), 4806–4814. Mizera, J., Mizerova, G., Machovic, V., Borecka, L., 2007. Sorption of cesium, cobalt and europium on low-rank coal and chitosan. Water Res. 41, 620–626.
7
Murat, T., Omer, S., Mustafa, I., 1997. Adsorption of cobalt by activated carbon from the rice hulls. J. Environ. Sci. Health 32, 2077–2086. Nelson, F., Phillips, H.O., Kraus, K.A., 1974. Adsorption of inorganic materials on activated carbon. Eng. Bull. Ext. Ser. 145, 1076–1090. Oliva, J., Pablo, J.D., Cortina, J.-L., Cama, J., Ayora, C., 2011. Removal of cadmium, copper, nickel, cobalt and mercury from water by Apatite IITM: column experiments. J. Hazard. Mater. 194, 312–323. Park, S., Mohanty, N., Suk, J.W., Nagaraja, A., An, J., Piner, R.D., Cai, W., Dreyer, D.R., Berry, V., Ruoff, R.S., 2010. Biocompatible, robust free-standing paper composed of a TWEEN/graphene composite. Adv. Mater. 22, 1736–1740. Posa, V.R., Annavaram, V., Koduru, J.R., Ammireddy, V.R., Somala, A.R., 2015. GrapheneZnO nanocomposite for highly efficient photocatalytic degradation of methyl orange dye under solar light irradiation. Korean J. Chem. Eng. 2015. http://dx.doi.org/10. 1007/s11814-015-0145-4 (Online). Prabhu, P.V.S.S., Narayana Swamy, M.S., Narasa Raju, T.S.S., 1981. Adsorption of zinc from aqueous solutions by fly ash. IAWPC Technical Annual report 8, pp. 46–52. Rengaraj, S., Moon, S.-H., 2002. Kinetics of adsorption of Co(II) removal from water and wastewater by ion exchange resins. Water Res. 36, 1783–1793. Sen, A.K., De, A.K., 1987. Adsorption of mercury(II) by coal fly ash. Water Res. 21, 885–888. Sigworth, E.A., Smith, S.B., 1972. Adsorption of inorganic compounds by activated carbon. J. Am. Water Works Assoc. 64, 386–391. Sitko, R., Turek, E., Zawisza, B., Malicka, E., Talik, E., Heimann, J., Gagor, A., Feist, B., Wrzalik, R., 2013. Adsorption of divalent metal ions from aqueous solutions using graphene oxide. Dalton Trans. 42, 5682–5689. Song, J., Wang, X., Chang, C.-T., 2014. Preparation and characterization of graphene oxide. J. Nanomater. 2014, 276143 (6 pp.). Srivastava, R.R., Kim, M.-S., Lee, J.-C., 2013. Separation of tungsten from Mo-rich leach liquor by adsorption onto a typical Fe–Mn cake: kinetics, equilibrium, mechanism, and thermodynamics studies. Ind. Eng. Chem. Res. 2013 (52), 17591–17597. Srivastava, R.R., Kim, M.-S., Lee, J.-C., Jha, M.K., Kim, B.-S., 2014. Resource recycling of superalloys and hydrometallurgical challenges. J. Mater. Sci. 49 (14), 4671–4686. Srivastava, R.R., Lee, J.-C., Kim, M.-S., 2015. Complexation chemistry in liquid–liquid extraction of rhenium. J. Chem. Technol. Biotechnol. 2015. http://dx.doi.org/10. 1002/jctb.4707. Tahir, S.S., Rauf, N., 2003. Thermodynamic studies of Ni(II) adsorption onto bentonite from aqueous solution. J. Chem. Thermodyn. 35 (12), 2003–2009. US Dept. of Energy report on Critical Materials Strategy, 2010. (December). Zhang, S., Guo, Z., Xu, J., Niu, H., Chen, Z., Xu, J., 2011. Effect of environmental conditions on the sorption of radiocobalt from aqueous solution to treated eggshell as biosorbent. J. Radioanal. Nucl. Chem. 288 (1), 121–130. Zhang, M., Zhu, G., Zhao, Y., Feng, X., 2012. A study of recovery of copper and cobalt from copper–cobalt oxide ores by ammonium salt roasting. Hydrometallurgy 129–130, 140–144.
Please cite this article as: Lingamdinne, L.P., et al., Adsorption removal of Co(II) from waste-water using graphene oxide, Hydrometallurgy (2015), http://dx.doi.org/10.1016/j.hydromet.2015.10.021